Field:
The present invention is directed toward a sterilizer with an improved drying phase, and particularly toward one in which a high-capacity vaporizing heater is operated subsequent to an exposure phase in a low-power mode to effect drying of a load.
State of the Art
Portable or self-contained sterilizers typically include an internal reservoir of water and a heater mounted at the bottom of the pressure vessel. The reservoir is typically filled with distilled water. A fixed amount or "charge" of water from the reservoir is dispensed into the pressure chamber for each sterilizing cycle. This charge of water fills the bottom of the chamber above an area heated by an electrical heating element. Water vaporization elements are necessarily of large capacity, typically from about 800 Watts to about 1800 Watts. The article to be sterilized, or "load," is subjected to an environment of pressurized, saturated steam. Sterilizers of this type are sometimes referred to as "table top" or "unplumbed" sterilizers.
After completion of the steam exposure phase of operation, it may be necessary to subject the load to a "drying phase," in which the chamber door is left ajar and dry heat is applied to the chamber. The water vaporizing element provides too much heat for this purpose. A low wattage heater (typically of fixed wattage between about 100 Watts to about 500 Watts) is thus conventionally mounted in the sterilizer. This low capacity heater is energized for a selected period of time to drive residual moisture from the load. The capacities of the vaporizing heater and the drying heater are selected on the basis of the size of the sterilizer vessel. The larger the vessel is, the higher the capacity for both the vaporizing heater and the drying heater. For example, a typical sterilizer may have a 1500 Watt vaporizing heater with a 150 Watt drying heater.
Such self-contained sterilizers, however, often do not provide adequate drying. Inadequate drying is particularly noticeable in the case of certain objects, such as sterilized instruments and wrapped instrument packs. During the sterilization process, steam typically penetrates the wrapped loads and condenses on instruments. After sterilization, this residual moisture must be removed or driven out of the packs to effect a complete sterilization.
Currently used drying systems also allow for inconsistent and incomplete results due to the many variables in the process. Such variables include, for example, how far the door is left open, AC line voltage, chamber temperature, the size and mass of the load, and air flow within the chamber. If a time period has elapsed between the exposure phase and the drying phase, the sterilizer, the load, and any condensed water may have cooled to room temperature. A low-wattage heater may be slow or ineffective in warming the load and the condensed water to a proper drying temperature.
There remains a need for a pressure chamber or sterilizer which provides for an improved drying phase and which eliminates the need for a separate low-power drying heater.